Maybe he knew he was off, which does make him seem pretty unprofessional if so, but if he'd fancied the move to Italy for a while he might not have wanted to fuck it up with an injury. That is me doing a bit of a Footy impersonation but you never know!
I think Tielemans has a higher ceiling than Luiz. I was extremely disappointed with Doug for most of the season after Christmas, his form seemed to vary between average and terrible.
One thing if you look back at the teams that Emery has built rather than inherited is that he does seem to like at least one big, tough midfielder to break up play in the way that none of our current midfielders really do. His Sevilla midfield was three 6ft+ brutes and anything creative that they did was of secondary importance. I wonder if he looks at our current options and thinks that while our passing options in midfield are pretty well set, he wants something bigger and nastier in DL's position and we're happy to sacrifice his playmaking for more strength and solidity.